<template>
    <select v-model="option" style="margin: 10px;">
        <option value="man">男</option>
        <option value="woman">女</option>
    </select>
</template>

<script>
export default {
    data() {
        return {
            option: "man"
        }
    },

    watch: {
        option: function (new_value, old_value) {
            console.log("v-model=option", new_value);
        }
    }
}
</script>